Preparation and characterization of poly (vinyl chloride)-blend-poly (carbonate) heterogeneous cation exchange membrane: Investigation of solvent type and ratio effects

In this research polyvinylchloride/polycarbonate blend heterogeneous cation exchange membranes were prepared by solution casting technique using cation exchange resin powder as functional groups agent. Tetrahydrofuran (THF) and dimethylformamide (DMF) were utilized as solvents. The effect of solvent type and ratio (THF/DMF mixture) on properties of prepared membranes was studied. SEM and SOM images showed relatively uniform particle distribution and also uniform surface for the membranes. Images showed that at high DMF ratio decrease of polymer conformation with particles surface reduces the compatibility of polymer-particle. The membrane ion exchange capacity and permeability were enhanced initially by increase of DMF ratio up to 5% (v/v) in casting solution and then they began to decrease with more DMF ratio. Results showed that membrane potential, transport number, selectivity and thermal stability all were decreased by DMF ratio increasing. Conversely, membrane water content, specific surface area and roughness showed opposite trends. Membrane electrical resistance initially declined by increase in DMF content up to 15% (v/v) and then it began to increase. The increase of electrolyte concentration also led to decrease in membrane transport number and selectivity. Membrane with (95:5) (v/v) solvent ratio (THF:DMF) exhibited more appropriate performance compared to others.